Various types of printing machines, and especially five-cylinder printing machines, require selective positioning of a printing cylinder in more than one position. In five-cylinder printing machines, having two plate cylinder-blanket cylinder couples and an impression cylinder, it is frequently desired to selectively engage a blanket cylinder with another blanket cylinder or with the impression cylinder to provide, selectively, double prime or prime-and-verso printing Repositioning of printing cylinders is usually accomplished by retaining the shafts defining the centers of rotation of the printing cylinders in bearings which are located in bearing supports eccentric with respect to the shaft. Upon moving the bearing support, the position of the shaft, and hence of the cylinder with respect to another cylinder will be changed.
It has previously been proposed--see German Pat. No. 1,238,929 to which British No. 1,158,470 corresponds--to so support a rubber blanket cylinder of a five-cylinder printing machine such that the rubber blanket cylinder can either be engaged with another rubber blanket cylinder for two-color prime printing, also referred to as 2/0 printing or to engage that blanket cylinder with an impression cylinder for single color prime-and-verso printing, referred to as 1/1 printing. Change-over between the rubber or blanket positioning cylinder positions is carried out while the machine is stopped. The change-over mechanism is comparatively complex. In order to change over the position of the blanket cylinder, the machine is first stopped, and the plate cylinder is moved out-of-engagement with the blanket cylinder with which it forms a couple. Then a bolt coupling or clutch is released from an engaged position, a pinion and a crank arm together with a flanged bushing is then brought into an intermediate position, about 90.degree. offset with respect to the initial position. The bolt is then engaged again, and an auxiliary drive is operated in order to move the blanket cylinder in the new position with the appropriate angular or rotary position to provide for engagement of the drive gear teeth against the impression cylinder, for example, from which it is driven. Thereafter, the coupling bolt is again released, the engagement movement further continued until the desired position is reached, and then the coupling bolt is again engaged in the third fixed and final position. Printing can be started only after a hydraulic cylinder controls the position of the respective blanket cylinder as desired, and, only then, can the machine be restarted.
The change-over, due to the dependence of the changed movement on the position of the engagement of the bolt on the one hand and the thus required release of the mechanism to engage and disengage the cylinder from the repositioning apparatus requires a considerable period of time, as well as skill and careful attention to monitor the position of the cylinders. The cylinders cannot be moved merely by hand, since they are steel elements which are very heavy.